#define  _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

size_t my_strlen(char* str)
{
	size_t count = 0;
	if (str == NULL) {
		return 0;
	}
	while (*str != '\0')
	{
		count++;
		str++;
	}
	return count;
}

int main()
{
	char str1[] = "hello world";
	size_t n=my_strlen(str1);
	printf("%zd", n);
	return 0;
}